Reduced TiO2 Nanotubes/Silk Fibroin/ZnO as a Promising Hybrid Antibacterial Coating

The influence of reduction process of TiO₂ nanostructures on the surface properties of a bioinspired Ti modified implant is elucidated in this work, considering that the interface between a biomaterial surface and the living tissue plays an important role for this interaction. The more conductive surfaces provided by the presence of RNT on Ti, allow a facile deposition of silk fibroin film. This hybrid film is then functionalized with ZnO nanoparticles, to improve the antibacterial effect of the coating. The antibacterial activity is studied for new created surfaces against S. aureus and E. coli.

Abstract

The current research aims to elucidate the influence of reduction process of TiO₂ nanostructures on the surface properties of a bioinspired Ti modified implant, considering that the interface between a biomaterial surface and the living tissue plays an important role for this interaction. The production of reduced TiO₂ nanotubes (RNT) with lower band gap is optimized and their performance is compared with those of simple TiO₂ nanotubes (NT). The more conductive surfaces provided by the presence of RNT on Ti, allow a facile deposition of silk fibroin (SF) film using the electrochemical deposition method. This hybrid film is then functionalized with ZnO nanoparticles, to improve the antibacterial effect of the coating. The modified Ti surface is evaluated in terms of surface chemistry, morphology and roughness, wettability, surface energy, surface charge and antibacterial properties. Surface analysis such as SEM, AFM, FTIR and contact angle measurements were performed to obtain topographical features and wettability. FT-IR analysis confirms that SF was effectively attached to TiO₂ nanotubes surfaces. The electrochemical deposition of SF and SF-ZnO reduced the interior diameter of nanotubes from ~85 nm to approx. 50–60 nm. All modified surfaces have a hydrophilic character.

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